What Is VXLAN? Encapsulation and Operation

April 15, 2026·1 min read·136 words

VXLAN (Virtual Extensible LAN) is the standard overlay protocol that extends L2 over L3 through UDP/IP encapsulation. Its 24-bit VNI supports 16M segments (vs 4094 VLANs). It is the de facto standard for modern data centers using EVPN. This quick guide explains the essentials.

How It Works

VTEP: switch/server that encapsulates and decapsulates VXLAN traffic
VNI (VXLAN Network Identifier): 24 bits (16M vs 4094 VLANs)
Standard UDP port 4789
Overhead: 50 bytes (jumbo MTU 9000 recommended for the underlay)

Control Plane

Flood and Learn: legacy approach that does not scale
BGP EVPN: modern standard for distributing MAC information and routes

Use Cases

Spine-leaf data centers
Stretched L2 between data centers (DCI)
Multi-tenant hosting providers
Kubernetes networking overlay

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Frequently Asked Questions

VXLAN remplace VLAN ?

Oui pour les data centers modernes. VXLAN supporte 16 millions de réseaux (VNI 24 bits) vs 4096 VLANs (12 bits). Plus important, VXLAN fonctionne sur un transport L3, ce qui permet la mobilité workload sans contrainte topologique.

Faut-il EVPN avec VXLAN ?

Pas obligatoire mais fortement recommandé. EVPN remplace le mode flood-and-learn (qui inonde le réseau) par un control plane BGP (publication MAC/IP via Type-2 routes). EVPN-VXLAN est le standard data center moderne.

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